What is the right answer for the riddle: Divided by a wall? (written by Mc Kevin)

I remember hearing this riddle when I was young.

Divided by a wall, N and S.
Tunnels in between, but no one can pass(through me).

The West has more(of me), and the East has less(of me).
Less is more, but More is less.

What am I, can you guess?

Hint 1:

I have a rectangular border